1. Field of the Invention
The present invention relates to gain-controlled amplifier techniques, and more particularly, to a gain-controlled amplifier having high linearity and high response speed, and capable of providing a negative gain.
2. Description of the Prior Art
A gain-controlled amplifier is a widely used circuit, which is designed according to practical applications. In general, three major design parameters are considered for a gain-controlled amplifier, linearity, response speed, and gain controllable range. As is well known, it is difficult to have the gain-controlled amplifier possess high linearity, high response speed, and wide gain controllable range all at the same time. For example, high linearity may be reached by utilizing an operational amplifier to implement the gain-controlled amplifier at the expense of response speed.